1. Technical Field
The present disclosure relates to measurement apparatuses and methods and, more particularly, to the qualitative and quantitative mapping of ionic diffusion and electrochemical transformations in materials using scanning probe microscopy and related methods on the nanometer scale.
2. Related Art
Electrochemical energy conversion systems based on gas-solid interactions, including fuel cells and metal-air batteries are of high priority in several areas of research and industry, for example, vehicular technologies and large-scale energy production from bio-fuels and fossil fuels. Implementation of fuel cells may be limited by relatively low power densities. However, energy densities may rival those of energy combustion engines. Since metal-air batteries possess slow charge and discharge rates, low power densities, limited number of charge and discharge cycles (fading), and energy densities well below what is theoretically possible, may occur. The last decade has seen an intensive effort to understand atomistic and mesoscopic mechanisms which are involved in battery and fuel cell development. This effort was driven by a goal to improve energy and power densities, device life times and high-voltage materials and systems.
The operation of energy conversion and storage systems is underpinned by a series of complex mechanisms, most prominently including ion and vacancy diffusion, electronic transport, solid-gas reactions and solid-liquid reactions at surfaces and triple-phase junctions. These processes may be controlled by structural defects and morphologic features of material that provide channels for ion and electron transport and reactive sites for electrochemical reactions. A recognized example of such behavior is electrocatalysis and triple-phase junction behavior in fuel-cell materials. This behavior directly underpins functionality and is virtually inaccessible to conventional microscopic and surface-science methods. However, even for materials and devices where vacancy formation and local reactivity are not a primary functionality, for example, in lithium insertion chemistries, they often determine pathways and localization of stray electrochemical reactions and processes and thus, may determine the life-time of a device. The importance of these considerations may be readily illustrated by the fact that relatively low-voltage, low energy density, but highly stable olivine cathodes currently dominate the automotive energy storage markets.